If you use it only when you really need to wash your hair and do scalp massaging in between
washes to extend the times between
washes, you'll find either one of these brands will last you longer than ordinary shampoo.
For deep conditioning, olive oil or coconut oil under a shower cap--overnight if you can stand it. Less if you can't. I usually do that then not shampoo it out but massage it under the shower. Very dry hair and scalp.